mynetworks rules don't appear to be working

[list]

In mynetworks I have the following IP configured (among others):

204.9.157.0/24          OK

In main.cf mynetworks is listed in the recipient restrictions:

smtpd_recipient_restrictions =
        permit_mynetworks,
        check_client_access hash:/etc/postfix/popimap_access,
        permit_sasl_authenticated,
        reject_unauth_destination

However I am getting relay denied errors for clients using an IP in that
range:

Nov  3 08:38:11 10.123.162.247 postfix/smtpd[20007]: NOQUEUE: reject: RCPT
from unknown[204.9.157.147]: 554 5.7.1 <tpeder3...@aol.com>: Relay access
denied; from=<sentr...@spwl.net> to=<tpeder3...@aol.com> proto=ESMTP
helo=<SentryHR>
Nov  3 10:03:13 10.123.162.247 postfix/smtpd[27180]: NOQUEUE: reject: RCPT
from unknown[204.9.157.147]: 554 5.7.1 <ksand...@amfam.com>: Relay access
denied; from=<sentr...@spwl.net> to=<ksand...@amfam.com> proto=ESMTP
helo=<SentryHR>
Nov  3 10:03:14 10.123.162.247 postfix/smtpd[27180]: NOQUEUE: reject: RCPT
from unknown[204.9.157.147]: 554 5.7.1 <tina.neh...@tdstelecom.com>: Relay
access denied; from=<sentr...@spwl.net> to=<tina.neh...@tdstelecom.com>
proto=ESMTP helo=<SentryHR>
Nov  3 10:25:00 10.123.162.247 postfix/smtpd[29112]: NOQUEUE: reject: RCPT
from unknown[204.9.157.147]: 554 5.7.1 <ksand...@amfam.com>: Relay access
denied; from=<sentr...@spwl.net> to=<ksand...@amfam.com> proto=ESMTP
helo=<SentryHR>
Nov  3 10:25:00 10.123.162.247 postfix/smtpd[29112]: NOQUEUE: reject: RCPT
from unknown[204.9.157.147]: 554 5.7.1 <tina.neh...@tdstelecom.com>: Relay
access denied; from=<sentr...@spwl.net> to=<tina.neh...@tdstelecom.com>
proto=ESMTP helo=<SentryHR>
Nov  3 10:25:00 10.123.162.247 postfix/smtpd[29112]: NOQUEUE: reject: RCPT
from unknown[204.9.157.147]: 554 5.7.1 <sentr...@spwl.net>: Relay access
denied; from=<sentr...@spwl.net> to=<sentr...@spwl.net> proto=ESMTP
helo=<SentryHR>
Nov  3 10:25:55 10.123.162.246 postfix/smtpd[7212]: NOQUEUE: reject: RCPT
from unknown[204.9.157.147]: 554 5.7.1 <n...@spwl.net>: Relay access denied;
from=<sentr...@spwl.net> to=<n...@spwl.net> proto=ESMTP helo=<SentryHR>
Nov  3 10:29:43 10.123.162.247 postfix/smtpd[29439]: NOQUEUE: reject: RCPT
from unknown[204.9.157.147]: 554 5.7.1 <sentr...@spwl.net>: Relay access
denied; from=<sen...@spwl.net> to=<sentr...@spwl.net> proto=ESMTP
helo=<Computer2>
Nov  3 10:31:29 10.123.162.247 postfix/smtpd[29607]: NOQUEUE: reject: RCPT
from unknown[204.9.157.147]: 554 5.7.1 <sentr...@spwl.net>: Relay access
denied; from=<n...@spwl.net> to=<sentr...@spwl.net> proto=ESMTP
helo=<pcnate>
Nov  3 10:55:11 10.123.162.247 postfix/smtpd[31698]: NOQUEUE: reject: RCPT
from unknown[204.9.157.147]: 554 5.7.1 <ksand...@amfam.com>: Relay access
denied; from=<sentr...@spwl.net> to=<ksand...@amfam.com> proto=ESMTP
helo=<SentryHR>
Nov  3 10:55:11 10.123.162.247 postfix/smtpd[31698]: NOQUEUE: reject: RCPT
from unknown[204.9.157.147]: 554 5.7.1 <tina.neh...@tdstelecom.com>: Relay
access denied; from=<sentr...@spwl.net> to=<tina.neh...@tdstelecom.com>
proto=ESMTP helo=<SentryHR>
Nov  3 11:23:07 10.123.162.246 postfix/smtpd[12211]: NOQUEUE: reject: RCPT
from unknown[204.9.157.147]: 554 5.7.1 <n...@spwl.net>: Relay access denied;
from=<sentr...@spwl.net> to=<n...@spwl.net> proto=ESMTP helo=<SentryHR>

Thanks in advance.